This invention is generally directed to toner and developer compositions, and more specifically the present invention is directed to processes for pigment, especially colored pigment dispersion in toner compositions, including magnetic, single component, and colored toner compositions by the utilization of polymeric alcohol waxes. In one embodiment, the process of the present invention enables improved pigment dispersion with toner compositions which are comprised of resin particles, pigment particles, and waxes with hydroxyl functionality, reference U.S. Pat. No. 4,883,736 issued Nov. 28, 1989, the disclosure of which is totally incorporated herein by reference. There is also provided in accordance with the present invention processes for improved pigment dispersion with positively or negatively charged toner compositions comprised of resin particles, pigment particles, and charge enhancing additives. Furthermore, there is provided in accordance with the present invention processes for pigment dispersion with toner compositions wherein the polymeric alcohol waxes are preferably present therein as internal additives. In an embodiment, the present invention is directed to processes for improved pigment dispersion with developer compositions comprised of the aforementioned toners, and carrier particles. Furthermore, in another embodiment of the present invention there are provided single component toner compositions comprised of resin particles, magnetic components such as magnetites, and waxes with hydroxyl functionality. The toner and developer compositions illustrated herein are useful in electrostatographic imaging systems, especially those systems wherein blade cleaning of the photoconductive member is accomplished. Moreover, the toner and developer compositions of the present invention enable the photoconductive imaging member present in an imaging apparatus to function for extended time periods, for example, up to 100,000 cycles while simultaneously preventing the localized accumulation of undersirable toner debris thereon which can encompass sufficient areas of the photoconductive members to permitting unwanted toner spots to be present on the final developed output copy. Further, the developer compositions of the present invention in an embodiment thereof possess stable electrical properties for extended time periods, and with these compositions, for example, there is no substantial change in the triboelectrical charging values, and substantially no degradation in A.sub.t which is the product of the toner concentration +1 multiplied by the triboelectric charging value. Therefore, the units of measurement (.mu.c percent/grams) for A.sub.t are .+-. microcoulombs of charge on the toner particles multiplied by the percent toner concentration divided by grams of the toner particles that are separated from the developer composition by, for example, known blowing processes, which units are dependent on a number of factors inclusive of the composition of the carrier particles selected. Accordingly, thus the A.sub.t for the developer compositions of the present invention in an embodiment thereof remains at, for example, from about 60 to about 80 for 300,000 developed images or copies while simultaneously maintaining high copy quality for each of the aforementioned images. There is permitted with the compositions of the present invention a prolonged charge exchange capability thereby contributing to a more stable development system requiring less complex control systems, and reduced maintenance of the imaging apparatus within which the compositions are incorporated. In addition, the aforementioned compositions provide for an increase in the latitudes over which a blade cleaning system can operate thereby enabling a more reliable and simpler apparatus.
By increased latitude, it is intended to refer to the achievement of obtaining an increase in the range of the load or force applied to the blade between a lower value wherein cleaning will fail, and an upper value wherein the blade undesirably bends causing the tip thereof to remain out of contact with the imaging member. Moreover, with increased latitude there can be selected a broader range of imaging member cleaning blade thicknesses, and various blade orientations with respect to the imaging member.
Improved pigment dispersion refers in an embodiment of the present invention to obtaining uniform dispersion of pigments including carbon black, colored pigments such as red, blue, green, cyan, magenta, yellow, brown and mixtures thereof and wherein there is avoided or minimized the formation of pigment agglomerates or domains, rather the dispersion is substantially uniform. More specifically, with colored pigment in an embodiment of the present invention the dispersion thereof and the toner composition is very uniform with no agglomerations of particles having an average diameter of larger than about 0.5 micron as compared to, for example, pigment agglomerates of greater than an average diameter of 1.5 microns when the polymeric alcohol wax illustrated herein is not selected. Improved pigment dispersion in the toner compositions enables a number of advantages including superior color intensity for the resulting developed images and transparency efficiency, which results were evidenced by, for example, electron photomicrographs. Accordingly, in an embodiment of the present invention the toner compositions with the polymeric alcohol wax enable better transparency efficiency, improved color intensities and resolutions and permit lower concentrations of pigment to be selected especially with respect to obtaining effective color intensities for the images developed with the aforementioned toners.
Developer and toner compositions with certain waxes therein, and imaging proceses thereof are known. For example, there are disclosed in U.K. Patent Publication 1,442,835 toner compositions containing resin particles, and polyalkylene compounds, such as polyethylene and polypropylene of a molecular weight of from about 1,500 to 6,000, reference page 3, lines 97 to 119, which compositions prevent toner offsetting in electrostatic imaging processes. Additionally, the '835 publication discloses the addition of paraffin waxes together with, or without a metal salt of a fatty acid, reference page 2, lines 55 to 58. Also, many patents disclose the use of metal salts of fatty acids for incorporation into toner compositions, such as U.S. Pat. No. 3,655,374. Also, it is known that the aforementioned toner compositions with metal salts of fatty acids can be selected for electrostatic imaging methods wherein blade cleaning of the photoreceptor is accomplished, reference U.S. Pat. No. 3,635,704, issued Jan. 18, 1972, the disclosure of which is totally incorporated herein by reference. Additionally, there are illustrated in U.S. Pat. No. 3,983,045 three component developer compositions comprising toner particles, a friction reducing material, and a finely divided nonsmearable abrasive material, reference column 4, beginning at line 31. Examples of friction reducing materials include saturated or unsaturated, substituted or unsubstituted, fatty acids preferably of from 8 to 35 carbon atoms, or metal salts of such fatty acids; fatty alcohols corresponding to said acids; mono and polyhydric alcohol esters of said acids and corresponding amides; polyethylene glycols and methoxy-polyethylene glycols; terephthalic acids; and the like, reference column 7, lines 13 to 43. Toner compositions containing polymeric alcohol waxes are disclosed in U.S. Pat. No. 4,883,736, the disclosure of which is totally incorporated herein by reference, and these waxes can be selected for the processes of the present invention.
In a patentability search report the following U.S. Pat. Nos. were listed: 4,883,736, which discloses toners with a polymeric alcohol of the formula as recited in the Abstract of the Disclosure for example, and wherein the alcohol can be selected as an internal or external additive, see column 10 for example; 4,859,550 which discloses smear resistant image character recognition processes with toners comprised of a polymeric alcohol, reference for example the Abstract of the Disclosure; 4,656,111 discloses a pressure fixable toner with long carbon chain compounds, including fatty alcohols to enhance dispersion of a pigment in a toner, see column 4 for example; 3,234,017 discloses a long chain alcohol as a toner additive, see column 4 for example; 3,165,420, 3,236,776, and 4,535,049 relating to the addition of waxes to toners; and as background interest 3,652,315, 4,833,056, 4,855,207, and 4,910,114.
Described in U.S. Pat. No. 4,367,275 are methods of preventing offsetting of electrostatic images of the toner composition to the fuser roll, which toner subsequently offsets to supporting substrates such as papers wherein there is selected toner compositions containing specific external lubricants including various waxes, see column 5, lines 32 to 45.
Moreover, toner and developer compositions containing charge enhancing additives, especially additives which impart a positive charge to the toner resin, are well know. Thus, for example, there is described in U.S. Pat. No. 3,893,935 the use of certain quaternary ammonium salts as charge control agents for electrostatic toner compositions. There is also described in U.S. Pat. No. 2,986,521 reversal developer compositions comprised of toner resin particles coated with finely divided colloidal silica. According to the disclosure of this patent, the development of images on negatively charged surfaces is accomplished by applying a developer composition having a positively charged triboelectric relationship with respect to the colloidal silica. Further, there is illustrated in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, developer and toner compositions having incorporated therein as charge enhancing additives organic sulfate and sulfonate compositions; and in U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, positively charged toner compositions containing resin particles and pigment particles, and as a charge enhancing additive alkyl pyridinium compounds, inclusive of cetyl pyridinium chloride.
Other prior art disclosing positively charged toner compositions with charge enhancing additives include U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014 and 4,394,430, the disclosures of which are totally incorporated herein by reference.
There is a need for processes with improved pigment dispersion with toner compositions with certain waxes, which compositions are useful in electrostatic imaging processes. In addition, there is a need for processes that enable improved color pigment dispersion with toner and developer compositions that maintain their triboelectrical characteristics for extended time periods, exceeding for example 100,000 developed images. Furthermore, there is a need for processes that enable improved color pigment dispersion with single component toners, and low melting toner resins, that possess many of the aforementioned characteristics. Also, there is a need for processes that enable improved color pigment dispersion with toner and developer compositions with certain toxicologically safe and economical waxes therein that allow the aforementioned advantages, and other advantages to be obtained in embodiments of the present invention.